Chapter 1: Introduction to API Development

In today's digital landscape, efficiently creating APIs is essential for integrating systems and exposing capabilities. This article discusses strategies for effective API development, particularly focusing on the contract-first and contract-last methodologies.

When it comes to API creation, there are primarily two methodologies: the Contract-first approach and the Contract-last approach. The distinction lies in the process followed to build the API.

In a Contract-first approach, the contract's definition serves as the foundation. Regardless of the programming language or technology employed, this principle has remained constant since the early days of distributed systems, such as RMI and CORBA, and continues to be relevant with modern frameworks like gRPC and GraphQL.

The development process begins with establishing the contract between the service provider and the initial consumer. This entails outlining various elements, such as the purpose of operations, the fields associated with each operation, expected return information for different scenarios, and error reporting details.

Following this, the API design and implementation will align with the agreed-upon contract.

The Contract-first approach offers several benefits, as well as certain challenges. Notably, it is currently one of the most widely accepted methods for API development. Some advantages include:

• Minimizing Rework: By defining the contract upfront, teams can quickly ensure that all parties agree before any implementation begins, thus avoiding costly rework due to misunderstandings.
• Clear Role Separation: This method fosters a clear delineation of responsibilities between the provider and consumer teams. Once the contract is established, both teams can begin their respective work, and the consumer can utilize mocks to test various scenarios without waiting for the actual service to be developed.

However, the Contract-first approach does come with requirements that are not always easily met in real-world situations. Many theoretical methodologies and tips often fall short in practical applications. To illustrate this, consider this question:

Did you ever create an API where the final interface matched your initial design perfectly?

In my experience, the answer is "No." Many developers might argue that they design better contracts, but the issue is more about the practicalities of implementation. During the implementation phase, unforeseen factors often arise that necessitate adjustments to the initial design, leading to increased costs.

While investing additional time in the contract definition can reduce the likelihood of discrepancies, it cannot eliminate them entirely. Moreover, this extended focus can negatively affect overall efficiency.

Another critical point is that while separation of duties is beneficial, an elongated interface creation phase delays when teams can start their work.

Conversely, adopting a Contract-last approach may lead to even greater costs, as customers often do not see the API until it is fully implemented. Reflecting on this, ask yourself:

Have you ever shared a project with a client without them requesting changes?

The common response is "No." The costs associated with changes tend to escalate significantly the later they are identified in the development process, following an exponential rather than linear trend.

So, what should you do? Embrace the Contract-first approach while acknowledging the realities of development. Strive for the best possible contract definition, and if any factors arise that could impact the API, communicate them to all parties promptly. This embodies an iterative approach to API definition, which is entirely valid.

Let's face it: there is no universal solution that guarantees a smooth workflow. This complexity is part of what makes our work engaging. Each decision we make in our projects, much like in life, involves numerous variables and details that influence the elegant methodologies we encounter in articles, papers, or lectures.